DOS's (German Unexamined Laid-Open Applications) Nos. 2,122,991; 2,157,036; 2,163,873; and 2,441,484, and U.S. application Ser. No. 608,250, filed Aug. 27, 1975, now U.S. Pat. No. 4,090,021, describe the conversion of hydroxy-N-heterocycles into monomeric, soluble and frequently volatile O-trimethylsilyl-N-heterocycles by silylation with hexamethyldisilazane (HMDS) and/or trimethylsilyl chloride/pyridine or triethylamine. Related art is disclosed by H. Vorbrueggen in U.S. Pat. No. 3,983,104, incorporated herein by reference. Reactive alcoholic or phenolic hydroxy and/or phosphate groups simultaneously present in the molecule are also silylated during the reaction and thus are blocked.
Reaction of a thus-substituted, silylated or free hydroxy-N-heterocycle with ammonia, or a primary or secondary amine in the presence of excess HMDS and a Lewis acid results, after several hours of heating to 80.degree.-160.degree. C., in high yields of aminated products. If other reactive groups are present, e.g., a ribose residue in a nucleoside, it is merely necessary following the amination to remove O-trimethylsilyl groups on the hydroxy groups of the sugar and/or of the phosphoric acid residue by transsilylation with methanol.
U.S. Pat. No. 3,884,957 teaches conversion of aromatic and aliphatic carboxylic acids to their respective nitriles by reaction with hexamethyldisilazane (HMDS), hexamethylcyclotrisilazane (HTS), and octamethylcyclotetrasilazane (OTS) by heating to 200.degree.-230.degree. C. in the presence of a Lewis acid, e.g., AlCl.sub.3 and ZnCl.sub.2.